1. Field of Invention
This invention relates to polymer films. More particularly, this invention relates to ultrathin polyether sulfone polymer films and their production.
2. Prior Art
The preparation of various polymer films on a liquid support, such as water, is known. For example, U.S. Pat. No. 2,760,233 discloses a process for preparing curved sheets of synthetic resins by floating monomeric or prepolymeric synthetic resins on a liquid surface. Among the numerous resins listed as being suitable in the patent's process are polysulfones. However, no film thicknesses are disclosed.
In U.S. Pat. No. 4,008,203 and British Pat. No. 1,016,245, polyether sulfone films are disclosed. However, no film thicknesses are described.
In U.S. Pat. No. 4,108,837, polyether sulfone films having thicknesses of 1.0 mil or more are disclosed. However, the films are not ultrathin.
In U.S. Pat. No. 3,933,561 a process for manufacturing polymer films on a liquid surface is disclosed. Films with a thickness of less than one micron, for example, 0.1 microns (i.e. 1,000 angstroms), are reportedly prepared by the patent's process. The preferred class of polymers is polysulfones. However, suitable chlorinated solvents for preparing ultrathin, pinhole-free, polyether sulfone films having thicknesses of 400 angstroms or less are not specifically disclosed.
U.S. Pat. No. 3,551,244 discloses a process for preparing on a water surface films having a thickness between 0.05 and 5.0 microns (i.e. between 500 and 50,000 angstroms). The patent lists certain halogenated solvents, such as chloroform, as suitable solvents and states that polysulfone films can be made. However, suitable chlorinated solvents for casting pinhole-free, polyether sulfone films are not specifically disclosed.
U.S. Pat. No. 3,767,737 discloses a method for producing on a support liquid nonporous polymer membranes having thicknesses between 0.005 and 0.05 mils. Any polymer or copolymer capable of being cast as a film from solvents is allegedly suitable for use in the patent's process. However, polyether sulfone is not listed as one of the typically suitable polymers and appropriate chlorinated solvents for preparing pinhole-free, polyether sulfone films are not specifically disclosed.
U.S. Pat. Nos. 4,155,793, 4,279,855 and 4,374,891 disclose processes for preparing substantially void-free, ultrathin, permeable polymeric membranes of 500 angstroms or less. Natural or synthetic polymers are allegedly suitable for use in the patent's process. However, only films prepared from organopolysiloxane polycarbonate interpolymers mixed with polyphenylene oxide are disclosed in the examples. Polyether sulfone films are not disclosed.
Other patents, such as U.S. Pat. Nos. 2,631,334, 2,689,187, and 4,393,113 also disclose ultrathin polymeric films. However, no polyether sulfone films are disclosed.
In the prior art, the preparation of ultrathin, pinhole-free, polyether sulfone, free-standing films with thicknesses of less than 400 angstroms generally has not been disclosed. Usually, prior art polymer films with thicknesses of less than 400 angstroms that are cast contain holes or other macroscopic defects.
Accordingly, it is an object of this invention to prepare ultrathin, polyether sulfone polymer films.
It is a further object of this invention to prepare pinhole-free, polyether sulfone polymeric films.
It is also an object of this invention to prepare free-standing, polyether sulfone films having thicknesses of 400 angstroms or less.
These and other objects are obtained by the products and process of the present invention.